import java.io.PrintStream;
import java.util.Scanner;

import franck.cse5910.Mouse;
import franck.cse5910.Timing;

public class MouseSpeed 
{
	public static void main(String[] args) 
	{
		Scanner input = new Scanner(System.in);
		PrintStream output = System.out;
		
		// prompt the user
		output.println("Move your mouse immediately after");
		output.print("entering the width of the screen in centimeters: ");
		double width = input.nextDouble();
		//output.println(width);
		
		// get initial position of mouse cursor
		double initialX = Mouse.getX();
		double initialY = Mouse.getY();
		//output.printf("(%.1f, %.1f)%n", initialX, initialY);
		
		// pause 0.1 second
		final long DELAY = 100;
		Timing.pause(DELAY);
		
		// get final position of mouse cursor
		double finalX = Mouse.getX();
		double finalY = Mouse.getY();
		//output.printf("(%.1f, %.1f)%n", finalX, finalY);
		
		// compute distance in terms of pixels
		double deltaX = Math.abs(initialX - finalX);
		double deltaY = Math.abs(initialY - finalY);
		double distanceInPixels = Math.sqrt(Math.pow(deltaX, 2) + Math.pow(deltaY, 2));
		//output.println(distanceInPixels);
		
		// compute distance in cm
		double distanceInCentimers = distanceInPixels * width / Mouse.maxX();
		//output.println(distanceInCentimers);
		
		// compute speed in miles per hour
		final double CENTIMETERS_PER_MILE = 100 * 1609.34;
		final int MILLISECONDS_PER_HOUR = 1000 * 60 * 60;
		double speed = (distanceInCentimers * MILLISECONDS_PER_HOUR) / (CENTIMETERS_PER_MILE * DELAY);
		assert speed >= 0;
		
		// print speed
		output.printf("%.2f%n", speed);
	}
}